Distannylated Bithiophene Imide: Enabling High‐Performance n‐Type Polymer Semiconductors with an Acceptor–Acceptor Backbone

Abstract

AbstractA distannylated electron‐deficient bithiophene imide (BTI‐Tin) monomer was synthesized and polymerized with imide‐functionalized co‐units to afford homopolymer PBTI and copolymer P(BTI‐BTI2), both featuring an acceptor–acceptor backbone with high molecular weight. Both polymers exhibited excellent unipolar n‐type character in transistors with electron mobility up to 2.60 cm2 V−1 s−1. When applied as acceptor materials in all‐polymer solar cells, PBTI and P(BTI‐BTI2) achieved high power‐conversion efficiency (PCE) of 6.67 % and 8.61 %, respectively. The PCE (6.67 %) of polymer PBTI, synthesized from the distannylated monomer, is much higher than that (0.14 %) of the same polymer PBTI*, synthesized from typical dibrominated monomer. The 8.61 % PCE of copolymer P(BTI‐BTI2) is also higher than those (<1 %) of homopolymers synthesized from dibrominated monomers. The results demonstrate the success of BTI‐Tin for accessing n‐type polymers with greatly improved device performance.